GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc5292

Network Working Group E. Chen Request for Comments: 5292 S. Sangli Category: Standards Track Cisco Systems

                                                          August 2008
        Address-Prefix-Based Outbound Route Filter for BGP-4

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Abstract

 This document defines a new Outbound Router Filter (ORF) type for
 BGP, termed "Address Prefix Outbound Route Filter", that can be used
 to perform address-prefix-based route filtering.  This ORF-type
 supports prefix-length- or range-based matching, wild-card-based
 address prefix matching, as well as the exact address prefix matching
 for address families.

1. Introduction

 The Outbound Route Filtering Capability defined in [BGP-ORF] provides
 a mechanism for a BGP speaker to send to its BGP peer a set of
 Outbound Route Filters (ORFs) that can be used by its peer to filter
 its outbound routing updates to the speaker.
 This documents defines a new ORF-type for BGP, termed "Address Prefix
 Outbound Route Filter (Address Prefix ORF)", that can be used to
 perform address-prefix-based route filtering.  The Address Prefix ORF
 supports prefix-length- or range-based matching, wild-card-based
 address prefix matching, as well as the exact address prefix matching
 for address families [BGP-MP].

2. Address Prefix ORF-Type

 The Address Prefix ORF-Type allows one to express ORFs in terms of
 address prefixes.  That is, it provides address-prefix-based route
 filtering, including prefix-length- or range-based matching, as well
 as wild-card address prefix matching.
 Conceptually, an Address Prefix ORF entry consists of the fields
 <Sequence, Match, Length, Prefix, Minlen, Maxlen>.

Chen & Sangli Standards Track [Page 1] RFC 5292 Address-Prefix-Based ORF for BGP-4 August 2008

 The "Sequence" field specifies the relative ordering of the entry
 among all the Address Prefix ORF entries.
 The "Match" field specifies whether this entry is "PERMIT" (value 0)
 or "DENY" (value 1).
 The "Length" field indicates the length (in bits) of the address
 prefix.  A length of zero indicates a prefix that matches all (as
 specified by the address family) addresses (with the prefix itself of
 zero octets).
 The "Prefix" field contains an address prefix of an address family.
 The "Minlen" field indicates the minimum prefix length (in bits) that
 is required for "matching".  The field is considered unspecified with
 a value of 0.
 The "Maxlen" field indicates the maximum prefix length (in bits) that
 is required for "matching".  The field is considered unspecified with
 a value of 0.
 The fields "Sequence", "Length", "Minlen", and "Maxlen" are all
 unsigned integers.
 This document imposes the following requirement on the values of
 these fields:
       0 <= Length < Minlen <= Maxlen
 However, tests related to the "Minlen" or "Maxlen" value should be
 omitted when the "Minlen" or "Maxlen" field (respectively) is
 unspecified.
 In addition, the "Maxlen" value must be no more than the maximum
 length (in bits) of a host address for a given address family
 [BGP-MP].

Chen & Sangli Standards Track [Page 2] RFC 5292 Address-Prefix-Based ORF for BGP-4 August 2008

3. Address Prefix ORF Encoding

 The value of the ORF-Type for the Address Prefix ORF-Type is 64.
 An Address Prefix ORF entry is encoded as follows.  The "Match" field
 of the entry is encoded in the "Match" field of the common part
 [BGP-ORF], and the remaining fields of the entry are encoded in the
 "Type specific part", as shown in Figure 1.
       +--------------------------------+
       |   Sequence (4 octets)          |
       +--------------------------------+
       |   Minlen   (1 octet)           |
       +--------------------------------+
       |   Maxlen   (1 octet)           |
       +--------------------------------+
       |   Length   (1 octet)           |
       +--------------------------------+
       |   Prefix   (variable length)   |
       +--------------------------------+
       Figure 1: Address Prefix ORF Encoding
 Note that the "Prefix" field contains the address prefix followed by
 enough trailing bits to make the end of the field fall on an octet
 boundary.  The value of the trailing bits is irrelevant.

4. Address Prefix ORF Matching

 In addition to the general matching rules defined in [BGP-ORF],
 several Address-Prefix-ORF-specific matching rules are defined as
 follows.
 Consider an Address Prefix ORF entry, and a route maintained by a BGP
 speaker with Network Layer Reachability Information (NLRI) in the
 form of <Prefix, Length>.
 The route is considered as "no match" to the ORF entry if the NLRI is
 neither more specific than, nor equal to, the <Prefix, Length> fields
 of the ORF entry.
 When the NLRI is either more specific than, or equal to, the <Prefix,
 Length> fields of the ORF entry, the route is considered as a match
 to the ORF entry only if the NLRI match condition as listed in Table
 1 is satisfied.

Chen & Sangli Standards Track [Page 3] RFC 5292 Address-Prefix-Based ORF for BGP-4 August 2008

           ORF Entry                  NLRI
      Minlen      Maxlen         Match Condition
    +------------------------------------------------------+
    | un-spec.    un-spec.       NLRI.length == ORF.length |
    +------------------------------------------------------+
    | specified   un-spec.       NLRI.length >= ORF.Minlen |
    +------------------------------------------------------+
    | un-spec.    specified      NLRI.length <= ORF.Maxlen |
    +------------------------------------------------------+
    | specified   specified      NLRI.length >= ORF.Minlen |
    |                        AND NLRI.length <= ORF.Maxlen |
    +------------------------------------------------------+
    Table 1: Address Prefix ORF Matching
 When more than one Address Prefix ORF entry matches the NLRI of the
 route, the "first-match" rule applies.  That is, the ORF entry with
 the smallest sequence number (among all the matching ORF entries) is
 considered as the sole match, and it would determine whether the
 route should be advertised.
 The assignment of the sequence numbers is a local matter for the BGP
 speaker that sends the Address Prefix ORF entries.

5. IANA Considerations

 This document specifies a new Outbound Route Filtering (ORF) type,
 Address Prefix ORF.  The value of the ORF-type is 64.

6. Security Considerations

 This extension to BGP does not change the underlying security issues
 in [BGP-4].

7. Normative References

 [BGP-4]   Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border
           Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.
 [BGP-MP]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
           "Multiprotocol Extensions for BGP-4", RFC 4760, January
           2007.
 [BGP-ORF] Chen, E., and Y. Rekhter, "Outbound Route Filtering
           Capability for BGP-4", RFC 5291, August 2008.

Chen & Sangli Standards Track [Page 4] RFC 5292 Address-Prefix-Based ORF for BGP-4 August 2008

Authors' Addresses

 Enke Chen
 Cisco Systems, Inc.
 170 W. Tasman Dr.
 San Jose, CA 95134
 EMail: enkechen@cisco.com
 Srihari R. Sangli
 Cisco Systems, Inc.
 170 W. Tasman Dr.
 San Jose, CA 95134
 EMail: rsrihari@cisco.com

Chen & Sangli Standards Track [Page 5] RFC 5292 Address-Prefix-Based ORF for BGP-4 August 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Chen & Sangli Standards Track [Page 6]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5292.txt · Last modified: 2008/08/05 00:48 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki